The Anglo-French decision to send a team of military advisers to Libyan opposition forces in Benghazi is a "clear violation" of the UN security council remit and will prolong the crisis engulfing the country, senior Libyan ministers have told the Guardian.

"It is a step to prolong the confrontation, there is no doubt about that," said Abdul Ati al-Obeidi, the foreign minister. "Sending military personnel will encourage the other side to be more defiant."

His deputy, Khaled Kayim, accused Nato and the international coalition of overstepping the security council resolution authorising military action to protect civilians, saying they were "siding with the rebels. Everything they have been doing since the start is outside the mandate."

He added: "No one can legitimise such actions. They will get nothing in return apart from more casualties. I think this is a big trap for Britain and France. They are dealing with the wrong groups. I can't understand why Britain and France are so keen to get themselves into trouble."

The two western countries would find themselves allied with al-Qaida forces, he said, which pro-Gaddafi forces claim are embedded with the rebels.

Fighting continued in Misrata and efforts intensified to bring in humanitarian aid and evacuate those trapped in the besieged city. The Libyan government denied any bombardment by its forces.

The Anglo-French move followed Nato air strikes, which destroyed three telecommunications installations around the city of Sirte on Monday, according to the Libyan government. Nato confirmed that communications infrastructure had been targeted and the headquarters of a Libyan army brigade.

Kayim said: "The aim is clear: to enable the rebels to advance and to cut communications between [government] troops."

The air strikes on communications centres came "at the same time as the British government sends very sophisticated telecommunications equipment to the rebels to enable them to organise themselves", Kayim told an earlier press conference in Tripoli. He added: "If Nato really cared about civilians, they have to stop the air strikes and stop siding with the rebels. Their aim is to push the country into a civil war. That's clear from day one."

He warned against any deployment of ground troops to protect humanitarian missions, as considered by the EU. "If there is any deployment of any armed personnel on Libyan ground, there will be fighting. The Libyan government will not take it as a humanitarian mission, it will be taken as a military mission," he said. "The Libyan people will not stay silent. They will join the armed forces and fight."

He said the Libyan government was doing its utmost "to help people and supply them with food", but he repeatedly declined to answer questions about whether Libya would agree to a pause in military action to allow humanitarian aid to reach the besieged city of Misrata.

"There is no need for such things. There is no bombardment from the armed forces on Misrata, none at all. There are pockets of resistance, but other areas are peaceful. There is no fighting in Misrata."

His claim contradicted witness accounts from inside the city and a Nato statement that Gaddafi's forces were shelling Misrata indiscriminately. Nato said its operations had inflicted "quite significant damage" to Libya's heavy weaponry while warning that Gaddafi's forces still had "considerable" resources left.

"But there is a limit to what can be achieved with airpower to stop fighting in a city. We are taking every precaution to avoid causing civilian casualties by our own air operations," said Brigadier General Mark Van Uhm at Nato headquarters in Brussels.

Admiral Giampaolo di Paola, chairman of Nato's military committee, speaking in Rome, said it was proving "very difficult" to strike against government forces in Misrata without inflicting civilian casualties. "It's not a conventional war," he added.

Witnesses in Misrata report that government snipers were firing from tall buildings and mosques.

The Libyan opposition claimed that 10,000 people had been killed since the start of the uprising, and more than 50,000 injured. It was unclear how casualty figures had been documented.

Opposition forces in Misrata say 1,000 people have been killed since the siege began in late February. More than 300 have been confirmed dead by the city's hospitals.

"This is all shit," Kayim said, claiming that the international coalition was exaggerating the number of casualties in Misrata.

Rebel leaders have warned the city may be lost within days without increased military action from Nato, and have appealed for troops to protect the passage of humanitarian aid through the bombarded port. The port is the only means of access to the area controlled by opposition forces.

The UN's World Food Programme said on Tuesday it had sent a convoy of eight trucks loaded with wheat flour and high-energy biscuits into government-controlled western Libya to reach areas affected by fighting. Battles between opposition forces and government troops have continued in the Western Mountains region, close to mountain near the Tunisian border.

Over the weekend, the UN reached agreement with the regime on carrying out aid operations in government-controlled areas. The UN said it has been promised access to Misrata, Libya's third largest city, but has received no guarantees from Libyan authorities that fighting would be halted to allow aid in.